1. Field of the Invention
This invention is in the field of cooling devices for particulate material, particularly for the cooling of cement clinker being discharged from a rotary kiln, and including at least two cooling systems in parallel relationship, with distributor means being used to selectively proportion the discharge of the rotary kiln between the two systems.
2. Description of the Prior Art
In German Pat. No. 917,716 there is described a rotary kiln which has two cooling devices connected consecutively, the first of which is connected adjacent the rotary kiln in the form of a step grate, and the second is a pipe cooler. As production is increased, however, there are problems of construction and operation both with the grate coolers as well as with the pipe cooler. For the attainment of a predetermined cooling effect in the pipe cooler, the gas velocity must be limited so that with increasing throughput of cooling material, very great pipe diameters must result. With such pipe coolers, the wear is increased through the increased dropping height which the more or less coarse materials being treated encounter in being rolled about in the cooling pipe. Because of the relatively low stability of shape of such very large cooling pipes, special construction means must be undertaken to provide stiffening of the pipe. Similarly, a grate cooler, with increasing output, requires a larger width and length, so that for a uniform cooling effect there must be a uniform material bed developed of a predetermined height. When the material to be cooled leaves the rotary kiln, however, in the form of a limited stream, special and usually very expensive means must be employed to make sure that there is a uniform distribution of the material to be cooled over the entire width of the grate. A non-uniform distribution of material results in obstructions, deposits, or caking, an impaired cooling effect, as well as an increased wear due, among other things, to local overheating. The utilization of a cooling apparatus in accordance with the aforesaid German Pat. No. 917,716 is economically feasible, because of the expenditure of maintenance and operational costs, only up to outputs or yields of approximately 2,500 metric tons per day.